Method of preparing organomercurials



Patented May 8, 1951 METHOD OF PREPARmG ORGANO- MERCURIALS Athey G. Gillaspie, Asheville, N. 0., assignor to The Hamilton Laboratories, Inc., Asheville, N. 0., a corporation of Delaware No Drawing. Application October 11, 1949, Serial No. 120,821

4 Claims. (01. 260-431) This invention relates to an improved chemical process for the preparation of water-soluble organomercurials and in particular it relates to the fusion of carboxylic acid amides and alkali salts of aliphatic acids with mercuric oxide or certain mercuric salts to produce highly soluble organomercurial compositions useful as bactericides and fungicides.

In accordance with the herein-described invention, a high yield of organomercurials free from reduced products is readily obtained by the simple expedient of fusing carboxylic acid amides and alkali salts of aliphatic acids with mercuric oxide at a temperature in the range of 80 to 160 C. Equimolecular quantities may be used or an excess of the amide or alkali salt may be employed in order to maintain a fluid system at a lower temperature.

The chief object of this invention is to provide a new process of producing soluble organomercurials useful as bactericides, fungicides, insecticides, and preservatives.

Another object is to provide a new organomercurial composition suitable for control of slime in the pulp and paper industry.

Another object is to provide an improved method of reacting amides and mercuric oxide whereby a very high yield of organomercurials is obtained.

Organic compounds of mercury have found extensive use as bactericides and fungicides because of their high potency. A number of these compounds have been employed in preventing the growth of slime in the papermaking industry. While only a relatively small amount of the mercurial, such as a phenylmercuric salt, is needed to control the slime,-the low solubility of these agents minimizes their effectiveness. When added in the convenient powder form the agent may not receive the necessary amount of agitation to become dissolved sufficiently to permit thorough distribution in the fiber suspension, or in the case of a high speed paper machine where the white water system is not a closed one, it may not be retained in the system long enough to be effective.

' One means resorted to in an attempt to overcome this difliculty has been the preparation of solutions of the organic mercury compounds which are then marketed to the user. Such solutions, however, are unstable, are corrosive, thereby requiring special containers and special handling precautions, are inconvenient to measure out, and impose an extra expense because of the added freight costs. In comparison, a bacteri-- instantly soluble in water and marketable as a powder, is obtained when mercuric oxide is reacted With a carboxylic acid amide and an aliphatic acid salt by fusion. While the organomercurials resulting from this reaction possess the general properties of mercurated amides, the reaction products are free from reduced forms of mercury and the mercuric oxide used is more completely converted into a soluble form than in the mercuration of amides in the absence of the alkali salts of aliphatic acids.

In the course of these studies I have found that aliphatic acids, such as acetic or propionic, or water, will promote the mercuration of acid amides at lower temperatures than are otherwise possible. Neither the acid nor the water, however, promotes the completeness of reaction that may be obtained by mixing an alkali salt of an aliphatic acid with the amide preparatory to mercuration- A to 99% conversion of mercuric oxide results, whereas in the absence of the aliphatic salt only about conversion can be secured. The reaction temperature is lowered at least 30 C. and virtually no decomposition products are formed. Furthermore, the salt of the aliphatic acid becomes an integral part of the product and contributes to its properties; in contrast, if water or acid is added to promote the mercuration, its separation from the product is necessary.

The product obtained by the herein-described fusion reaction is eminently suited as a slime control agent. One part of the product will dissolve in less than one part of water, Whereas slime control agents of the phenylmercuric type are soluble only to the extent of about one part in 400 to 20,000 parts of water. When used in the papermaking furnish in the ratio of one ounce to three tons of wood pulp (dry weight) it kept the heaters, pipes, chests, etc. free of slime and maintained the bacterial count of the paper well below the maximum allowable even in the summer months. The product of this invention because of its ready solubility possesses the advantages of instantaneous effectiveness and easy dispersal found in liquid slime control agents and at the same time can be marketed in dry forminprepared unit dosages. A further advan tage resides in the fact that my product has less tendency to react with the Fourdrinier wire than other mercurials.

My invention is illustrated by the following examples in which the parts are by weight:

Example 1 Sodium acetate, hydrate-In a vessel equipped with an agitator and external heating device, 30 parts of crystalline sodium acetate and 70 parts of acetamide, technical grade, were fused at 70 C. Heating was continued until a temperature of 135-14=0 C. was reached. Then 100 parts of mercuric oxide was added slowly and the system agitated until the water of reaction distilled off. The time required varies with the size of the batch and the efficiency of the agitation but generally is in the range of to 30 minutes. After cooling to room temperature, the melt, a brittle, gray solid, was ground to a powder and stored in a moistureproof container. The product on analysis showed 98% of the mercuric oxide had been converted into a water-soluble form. Aqueous solutions containing up to 60% dissolved solids can be formed of the product; the pH of the concentrated solution is about 6.9. The product is very effective against bacteria and fungi; the inhibiting concentration against Aerobacter aerogenes is about 1 part in 10 million. The product was used in a papermaking system containing bleached pine kraft pulp at a ratio of one ounce per three tons of wood pulp, dry basis; the system operated free of slime growth.

Example II Sodium acetate, aa'hydroas.-Twe1ve parts of this salt and 80 parts of acetamide, technical grade, were fused at 150-l55 C. To this melt was added 100 parts of mercuric oxide, with agitation, and the temperature was maintained for 10-12 minutes to vaporize the water of reaction. The melt was allowed to cool to room temperature and then ground to a powder. The product contained about 1% of insoluble material.

Example I I I Potassium acetate.Twenty parts of potassium acetate and 80 parts of acetamide, technical grade, were melted in a vessel with stirring, and held at 140-l50 C. while 100 parts of mercuric oxide were added. The fluid system was heated at the same temperature for 10-20 minutes to distill off the water of reaction. The cooled cake was ground to a powder and stored out of contact with moisture. The powder is slightly darker than that obtained by employing sodium acetate but is just as readily soluble and the yield of organomercurials is substantially th same.

Example IV Sodium propionate.Twenty parts of sodium propionate and 80 parts of acetamide, technical grade, were melted in a vessel equipped with means for agitation, 100 parts of mercuric oxide were stirred in, and the temperature was held at 140 to 150 C. for 20 minutes to remove water. The melt was solidified and then ground to a powder. This organomercurial powder is slightly less soluble than when sodium acetate is used. The yield was 98% based on the mercuric oxide used.

Example V Potassium and sodium acetate.-Four parts of potassium acetate and 8 parts of sodium acetate, anhydrous, were melted with 80 parts of acetamide, technical grade, the temperature was raised to 140150 C., agitation was applied, and parts of mercuric oxide was introduced. After the melt was agitated at this temperature for 20 minutes it was cooled, ground to a powder, and stored in a tight container. A 98% conversion of mercuric oxide to soluble mercurial was obtained. The melt containing potassium acetate and sodium acetate is more iiuid at the reaction temperature than a system that contains either one of the acetates alone.

Example V] In a vessel equipped with means for agitation and provision for external heating, '75 parts of acetamide, 5 parts of sodium acetate, anhydrous, and 20 parts of water are heated to C., and 100 parts of mercuric oxide is added slowly. Heat of reaction caused the temperature to rise to -120 C. Reaction was complet in 20 minutes. Water was then added to reduce the system to 60% total solids and the resulting solution pumped into a drum drier heated to C. The product was obtained as dry flakes.

It is understood that the foregoing examples are illustrative only and that other water-soluble acid amides can be used. Formamlde is satisfactory except that the reaction product is soft. Propionamide forms an acceptable solid but is somewhat mor expensive. When benzamide is employed the reaction mixture is relatively low in water solubility.

In place of mercuric oxide, mercuric acetate or propionate may be used in which case th acid evolved must be removed.

My preferred temperature range is to 160 C. At temperatures below 106 C. the water of reaction is removed slowly unless the melt is subject to reduced pressure. A further disadvantage of the lower temperature oi reaction is that more amide or sodium acetate is required to maintain a fluid medium. Above 160 C. decomposition of the desired organomercurlals occurs and is pronounced at temperatures of C. and above.

The reaction of mercuric oxide with acid amides and alkali salts of aliphatic acids is usually completed in five minutes agitation at the optimum temperatures as cited in the examples. It is obvious, however, that the removal of the water of reaction is a function of the temperature, the total reacting mass, and the rate of change of exposed surface.

The reaction product of this invention is suitable, as is, for use as a fungicide, bactericide, or the like, requiring no further processing or purification. There is substantially no insolubie matter, and what little there is does not detract from the slime-controlling properties. The sodium acetate exerts a beneficial action in th product, increasing its solubility and making it more effective against microorganisms, and in addition the aliphatic acid salt makes the drying and handling of the product practical.

I have found that the ratio of aliphatic acid salt (anhydrous basis) to amide should be in the range of 1:15 to 1:2, by weight. In the neighborhood of one part of sodium acetate to two parts of acetamide easy reaction and handling obtain; nothing is gained by the use of a larger proportion of the salt. Satisfactory mercuration can be obtained with as little as one part of sodium acetate to 15 parts of acetamide; however, drying of the reaction product becomes difficult in this range.

While equimolecular amounts of acid amide and mercuric oxide can be used, it is preferable to have an excess of th acide amide. Thus, with the substantially equimolecular proportions, 55 parts of acetamide, and 100 parts of mercuric oxide, and with 5 parts of sodium acetate present, the reaction is about 80% complete at temperatures such as cited in the examples. By changing the amount of acetamide to '70 parts, the other conditions remaining the same, the reaction goes to substantial completion. No noticeable benefits are derived by using more than 80 parts of acetamide.

The salts of aliphatic acids which are suitable for carrying out the fusion reaction comprise the lithium, sodium, potassium, rubidium, and caesiu-m acetates, propionates, and butyrates. The aliphatic acid salts above the butyrates have insufficient water solubility. Th formates are less suitable because of their reducing properties.

I claim:

1. Method of preparing organomercurials which comprises reacting by fusion a carboxylic acid amide with mercuric oxide in the presence of alkali metal salt of an aliphatic acid.

2. Method of preparing organomercurials which REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Kharasch Dec, '7, 1943 OTHER REFERENCES J. American Chem. Soc. 64, 1738-9, 1942.

Number 

1. METHOD OF PREPARING ORGANOMERCURIALS WHICH COMPRISES REACTING BY FUSION A CARBOXYLIC ACID AMIDE WITH MERCURIC OXIDE IN THE PRESENCE OF ALKALI METAL SALT OF AN ALIPHATIC ACID. 